Five essential things to know about evolution

If the public doesn't get evolution, part of the reason may be because many …

If scientists had to pick one area of science that's most frequently misunderstood, evolution would probably win the vote. It's not simply the sea of misinformation available on the Internet (although that clearly doesn't help); it also seems that a lot of people who accept the scientific evidence don't fully appreciate some aspects of evolutionary theory. It's one thing to remember a few examples of the compelling evidence we have for evolution; it's another thing entirely to appreciate the features of the process that make it so incredibly powerful but, at the same time, hide many of its actions from our common experience.

So, in a slight change of pace, we're going to skip focusing on the latest results or a comprehensive review of the evidence (we've done quite a bit of that in the past), and focus instead on some of the general aspects of the theory, many of which are commonly overlooked. So, without further ado, we present five things you may not know about evolution.

A really inefficient solution can be a lot better than the alternative

This is especially true when the alternative is "dead." People tend to evaluate evolution according to what, for the time being, at least, are its finished products: highly efficient enzymes, mind-numbingly complex structures, and other biological wonders. But it's important to remember that the structures we see around us today are the products of millions of years—in some cases, billions of years—of fine tuning. The original solutions were probably anything but elegant.

A great example is the protein that eliminates reactive oxygen within our cells. For a billion years or more, organisms didn't really have to deal with oxygen, which only became prevalent after the origin of photosynthesis. But when oxygen arrived, it was presumably a shock to the system, as it was toxic to some organisms, and reactive oxygen could damage a variety of cellular components. Organisms had to evolve the ability to cope with it or, quite possibly, die.

It turns out that a single change is sufficient to convert an enzyme that normally operates on hydrocarbons to one that can eliminate oxygen radicals. It does this really, really poorly in comparison with its current-day descendants, which have been improved by billions of years of refinement. But really, really poorly is pretty good when you're dealing with something that might otherwise kill you. And survival is all that's needed for evolutionary refinements to take place.

Evolution solves problems in parallel

Humans have a tendency to think from a linear, one-thing-at-a-time perspective. So, when we think of all the different things that happen during an evolutionary transition, we tend to compile them into a long, linear list. So, for the case of, say, the divergence of humans from our common ancestor with chimps, we'd compile something that included behavioral differences, upright walking, altered shoulder structure, bigger brains, etc. When you look down that list, six million years suddenly seems like a very short span of time.

But it's not like the entire rest of the genome sat still while our ancestors were evolving the ability to digest lactose as adults. For the most part, evolution of a given useful trait can (and does) occur in parallel with anything else that's happening. There are some dependencies—rearranging the foot doesn't make much sense unless you're already walking upright—but it can certainly occur at the same time as all the behavioral changes, dietary changes, etc.

An additional consequence of this is that related problems can be solved in a coordinated manner. A lot of human evolutionary history involved a balancing act between the hip structure that allows us to walk upright efficiently and a brain size that doesn't fit through said hips very well. The net result is that neither of these changed radically, even between ancestors that we consider different species.

Evolution doesn't happen overnight

So, with all that working in its favor, shouldn't we be seeing evolution changing the world around us as we watch? It's easy to forget that a favorable novelty starts out as just one change in one individual. To get beyond that individual, their offspring have to be lucky enough to inherit it, reproduce, etc. before it can even spread within a small, localized population.

For animals that we pay attention to, generation times are a year or more. Even if most evolutionary change wasn't gradual, the flow of genes from individual to a population would necessarily take time for precisely this reason.

Another thing that most people also don't realize is that if a genetic change truly is favorable, its ability to spread to within populations is a mathematical necessity. There's an entire field (population genetics) devoted precisely to this issue that, unfortunately, rarely receives any attention, even in college-level genetics classes. A lot of the work dates from the 1930s and involves lots of math, so this is somewhat understandable now that the focus of biology has shifted to the genome. But population genetics essentially showed how Mendelian genetics enabled evolution, a reconciliation so significant that it's still referred to as the "Modern Synthesis."

A million years is a lot longer than we think it is

Evolution may take time, but there has been a lot more time available than most of us fully appreciate. The major evolutionary transitions, which took place over millions of years or more, still account for a tiny fraction of the history of life on earth. Most of us kind of know that, but it's difficult to really comprehensively understand what millions of years mean. All of recorded human history? That's less than a tenth of the time since modern humans left Africa. Which is only about a tenth of a million years. Which is less than a quarter of the time since our ancestors last canoodled with those of the chimps a bit over four million years ago.

All of recorded human experience is just a blink of an eye, and yet we've seen hundreds of extinctions, dozens of speciations, observed speciation happen in the lab, watched entire ecosystems change, and driven quite a lot of these changes ourselves. If you really have a grasp of evolutionary time, then the question isn't one of "did evolution result in the origin of species"—it's too easily obvious that it did. Instead, the relevant question becomes one of why it produced the species we now see.

We wouldn't recognize a key transition while it was happening

So, if all this evolving is constantly going on, why don't we see species that seem to be in the midst of a major transition? Simple: we wouldn't know it if we were. Feathers on dinosaurs were around for many millions of years before any of them were able to glide, much less take flight using them. Pakicetus, although it lived on land, had skull features that indicate it was closely related to all whales and porpoises. It hung around Asia for millions of years, looking a bit like an odd relative of the wolf. The bones that now form our wrists first appeared inside the fins of fish, where variants of them appeared in a variety of species.

All these species, despite the novel features they contained, looked just like a normal part of the ecosystem at the time. Evolutionary changes occur gradually enough that there's really nothing distinctive about them at the time. It's only in retrospect, with our lands filled with tetrapods and skies filled with birds, that we're able to tell that the odd-looking fins and the dinosaurs with plumage were the start of something big. At the time, they'd look like nothing special; in fact, given that relatively few species wind up fossilized, some of them might have looked decidedly average, one of a large number of similar species.

These aren't even close to being the only misconceptions about evolution, but they're some of the most common—and the ones that most frequently leave the public expecting evidence for the theory that doesn't match its predictions.